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A combustion-powered, fastener-driving tool includes a cylinder and a combustion chamber disposed on top of the cylinder that accommodates a gaseous mixture of existing air in the combustion chamber and fuel injected therein. A spark plug generates a spark to combust the gaseous mixture in the combu

A combustion-powered, fastener-driving tool includes a cylinder and a combustion chamber disposed on top of the cylinder that accommodates a gaseous mixture of existing air in the combustion chamber and fuel injected therein. A spark plug generates a spark to combust the gaseous mixture in the combustion chamber. A trigger produces the spark in the spark plug when operated. A piston is movably supported in the cylinder and driven by combustion in the combustion chamber. A driving blade is coupled to the piston for driving a fastener. A spark controller is provided for generating a plurality of sparks in succession with the spark plug.

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What is claimed is: 1. A combustion-powered, fastener-driving tool comprising: a housing; a cylinder fixedly disposed in the housing; a combustion chamber disposed on top of the cylinder, the combustion chamber accommodating a gaseous mixture of existing air in the combustion chamber and fuel injec

What is claimed is: 1. A combustion-powered, fastener-driving tool comprising: a housing; a cylinder fixedly disposed in the housing; a combustion chamber disposed on top of the cylinder, the combustion chamber accommodating a gaseous mixture of existing air in the combustion chamber and fuel injected therein; a spark plug that is disposed in the combustion chamber and generates a spark to combust the gaseous mixture in the combustion chamber; a trigger that produces the spark in the spark plug when operated; a piston movably supported in the cylinder and driven by combustion in the combustion chamber; a driving blade coupled to the piston for driving a fastener; a spark controller that generates a plurality of sparks in succession with the spark plug; and a temperature sensor that detects a tool temperature that is primarily increased by heat generated in the combustion chamber; wherein the spark controller varies the number of sparks generated in the spark plug based on the temperature detected by the temperature sensor so as to provide at least one spark. 2. The combustion-powered, fastener-driving tool according to claim 1, wherein the spark controller varies the number of sparks so that when the tool temperature is lower than a predetermined level the number of sparks is set to be greater than the number of sparks when the tool temperature is higher than the predetermined level. 3. A combustion-powered, fastener-driving tool comprising: a housing; a cylinder fixedly disposed in the housing; a combustion chamber disposed on top of the cylinder, the combustion chamber accommodating a gaseous mixture of existing air in the combustion chamber and fuel injected therein; a spark plug that is disposed in the combustion chamber and generates a spark to combust the gaseous mixture in the combustion chamber; a trigger that produces the spark in the spark plug when operated; a piston movably supported in the cylinder and driven by combustion in the combustion chamber; a driving blade coupled to the piston for driving a fastener; and a spark controller that generates a plurality of sparks in succession with the spark plug; wherein the spark controller controls the spark plug to generate a first predetermined number of sparks when the tool temperature is within a predetermined range, a second predetermined number of sparks when the tool temperature is lower than lowest temperature in the predetermined range, and a third predetermined number of sparks when the tool temperature is higher than highest temperature in the predetermined range, and wherein the second predetermined number and the third predetermined number are greater than the first predetermined number. 4. The combustion-powered, fastener-driving tool according to claim 3, wherein the second predetermined number of sparks is greater than the third predetermined number of sparks. 5. A combustion-powered, fastener-driving tool comprising: a housing; a cylinder fixedly disposed in the housing; a combustion chamber disposed on top of the cylinder, the combustion chamber accommodating a gaseous mixture of existing air in the combustion chamber and fuel injected therein; a spark plug that is disposed in the combustion chamber and generates a spark to combust the gaseous mixture in the combustion chamber; a trigger that produces the spark in the spark plug when operated; a piston movably supported in the cylinder and driven by combustion in the combustion chamber; a driving blade coupled to the piston for driving a fastener; and a spark controller that generates a plurality of sparks in succession with the spark plug; wherein the spark controller comprises a spark capacitor charging circuit, and a spark energy accumulating capacitor connected to the spark capacitor charging circuit, the spark energy accumulating capacitor supplying energy to the spark plug to generate the spark, and wherein the spark capacitor charging circuit varies a charge time for charging the spark energy accumulating capacitor based on the number of sparks to be generated. 6. A combustion-powered, fastener-driving tool comprising: a housing; a cylinder fixedly disposed in the housing; a combustion chamber disposed on top of the cylinder, the combustion chamber accommodating a gaseous mixture of existing air in the combustion chamber and fuel injected therein; a spark plug that is disposed in the combustion chamber and generates a spark to combust the gaseous mixture in the combustion chamber; a trigger that produces the spark in the spark plug when operated; a piston movably supported in the cylinder and driven by combustion in the combustion chamber; a driving blade coupled to the piston for driving a fastener; and a spark controller that generates a plurality of sparks of at least two sparks in succession with the spark plug for combustion of the gaseous mixture; wherein the spark controller comprises a combustion sensor that is disposed in the housing, detects occurrence of combustion of the gaseous mixture in the combustion chamber, and outputs a detection signal indicative of occurrence of combustion, and wherein the spark controller cancels the generation of the plurality of sparks with the spark plug when the combustion sensor outputs the detection signal. 7. The combustion-powered, fastener-driving tool according to claim 6, wherein the spark controller varies the number of sparks generated in the spark plug based on the temperature detected by the temperature sensor so as to provide at least one spark. 8. A combustion-powered, fastener-driving tool comprising: a housing; a cylinder disposed in the housing and extending vertically; a piston vertically movably supported in the cylinder; a driving blade coupled to the piston for driving a fastener; a combustion chamber frame vertically slidably movable along the cylinder, a combustion chamber being formed on top of the cylinder by the combustion chamber frame and the piston, the combustion chamber accommodating a gaseous mixture of existing air in the combustion chamber and fuel injected therein; a spark plug that is disposed in the combustion chamber and generates a spark to combust the gaseous mixture in the combustion chamber; a trigger that produces the spark in the spark plug when operated; a spark controller that generates a plurality of sparks in succession with the spark plug; and a temperature sensor that detects a tool temperature that is primarily increased by heat generated in the combustion chamber; wherein the spark controller varies the number of sparks generated in the spark plug based on the temperature detected by the temperature sensor so as to provide at least one spark. 9. The combustion-powered, fastener-driving tool according to claim 8, wherein the spark controller varies the number of sparks so that when the tool temperature is lower than a predetermined level the number of sparks is set to be greater than the number of sparks when the tool temperature is higher than the predetermined level. 10. A combustion-powered, fastener-driving tool comprising: a housing; a cylinder disposed in the housing and extending vertically; a piston vertically movably supported in the cylinder; a driving blade coupled to the piston for driving a fastener; a combustion chamber frame vertically slidably movable along the cylinder, a combustion chamber being formed on top of the cylinder by the combustion chamber frame and the piston, the combustion chamber accommodating a gaseous mixture of existing air in the combustion chamber and fuel injected therein; a spark plug that is disposed in the combustion chamber and generates a spark to combust the gaseous mixture in the combustion chamber; a trigger that produces the spark in the spark plug when operated; and a spark controller that generates a plurality of sparks in succession with the spark plug; wherein the spark controller controls the spark plug to generate a first predetermined number of sparks when the tool temperature is within a predetermined range, a second predetermined number of sparks when the tool temperature is lower than lowest temperature in the predetermined range, and a third predetermined number of sparks when the tool temperature is higher than highest temperature in the predetermined range, and wherein the second predetermined number and the third predetermined number are greater than the first predetermined number. 11. The combustion-powered, fastener-driving tool according to claim 10, wherein the second predetermined number of sparks is greater than the third predetermined number of sparks. 12. A combustion-powered, fastener-driving tool comprising: a housing; a cylinder disposed in the housing and extending vertically; a piston vertically movably supported in the cylinder; a driving blade coupled to the piston for driving a fastener; a combustion chamber frame vertically slidably movable along the cylinder, a combustion chamber being formed on top of the cylinder by the combustion chamber frame and the piston, the combustion chamber accommodating a gaseous mixture of existing air in the combustion chamber and fuel injected therein; a spark plug that is disposed in the combustion chamber and generates a spark to combust the gaseous mixture in the combustion chamber; a trigger that produces the spark in the spark plug when operated; and a spark controller that generates a plurality of sparks in succession with the spark plug; wherein the spark controller comprises a spark coil having a primary winding and a secondary winding to which the spark plug is connected, and a spark energy accumulating capacitor connected to the primary winding of the spark coil for supplying energy to the spark plug to generate the spark, and wherein charging time of the spark energy accumulating capacitor is varied depending on the number of sparks to be generated. 13. A combustion-powered, fastener-driving tool comprising: a housing; a cylinder disposed in the housing and extending vertically; a piston vertically movably supported in the cylinder; a driving blade coupled to the piston for driving a fastener; a combustion chamber frame vertically slidably movable along the cylinder, a combustion chamber being formed on top of the cylinder by the combustion chamber frame and the piston, the combustion chamber accommodating a gaseous mixture of existing air in the combustion chamber and fuel injected therein; a spark plug that is disposed in the combustion chamber and generates a spark to combust the gaseous mixture in the combustion chamber; a trigger that produces the spark in the spark plug when operated; and a spark controller that generates a plurality of sparks of at least two sparks in succession with the spark plug for combustion of the gaseous mixture; wherein the spark controller comprises a combustion sensor that is disposed in the housing, detects occurrence of combustion of the gaseous mixture in the combustion chamber, and outputs a detection signal indicative of occurrence of combustion, and wherein the spark controller cancels the generation of the plurality of sparks with the spark plug when the combustion sensor outputs the detection signal. 14. The combustion-powered, fastener-driving tool according to claim 13, wherein the spark controller varies the number of sparks generated in the spark plug based on the temperature detected by the temperature sensor so as to provide at least one spark.